In general, compressors serving to compress refrigerant in vehicle cooling systems have been developed in various forms. The compressors are basically classified into a reciprocating compressor which performs compression by reciprocating motion and a rotary compressor which performs compression by rotary motion, according to a driving method.
There is a swash plate compressor as one type of the reciprocating compressor. The swash plate compressor includes a fixed capacity type swash plate compressor capable of fixing an installation angle of a swash plate and a variable capacity type swash plate compressor capable of changing an inclined angle of a swash plate so as to vary a discharge capacity.
FIG. 1 shows a configuration of a typical variable swash plate compressor. As shown in FIG. 1, a variable swash plate compressor 10 (hereinafter, referred to as “a compressor”) includes a cylinder block 20 defining a portion of an external appearance and frame of the compressor 10. A center bore 21 is formed by penetrating the middle of the cylinder block 20 and a rotary shaft 30 is rotatably installed to the center bore 21.
A plurality of cylinder bores 22 is radially arranged with respect to the center bore 21 so as to be formed by penetrating the cylinder block 20. A piston 23 is installed within each of the cylinder bores 22 so as to be capable of linearly reciprocating. The piston 23 has a cylindrical shape and the cylinder bore 22 is a cylindrical space corresponding to the same. Refrigerant is introduced into or compressed and discharged from the cylinder bore 22 by reciprocating motion of the piston 23.
A front housing 40 is coupled to the front of the cylinder block 20. The front housing 40 defines a crank chamber 41 therein together with the cylinder block 20.
A pulley 42 connected to an external power source (not shown) such as an engine by a belt is rotatably installed in the front of the front housing 40. The rotary shaft 30 is rotated along with rotation of the pulley 42.
A rear housing 50 is coupled to the rear of the cylinder block 20. A discharge chamber 51 is defined in the rear housing 50 along a position adjacent to an outer peripheral side edge of the rear housing 50, so as to selectively communicate with the associated cylinder bore 22. A suction chamber 52 is defined radially inward of the discharge chamber 51, namely, at a central portion of the rear housing 50.
In this case, a valve assembly, which includes a valve plate 60, and a suction reed plate and a discharge reed plate respectively installed on both side surfaces of the valve plate, is installed between the cylinder block 20 and the rear housing 50.
The discharge chamber 51 communicates with the associated cylinder bore 22 through each discharge port 61 formed at the valve plate 60 and the suction chamber 52 communicates with the associated cylinder bore 22 through each suction port 62 of the valve plate 60.
A rotor 70 is installed at one side of the rotary shaft 30 and integrally rotates with the rotary shaft 30 during rotation of the rotary shaft 30. The rotor 70 is installed within the crank chamber 41 such that the rotary shaft 30 passes through the middle of the crank chamber. A hinge section 71 is protrusively formed on one surface of the rotor 70.
A swash plate 80 is installed on the rotary shaft 30 in such a way to be spaced apart from the rotor 70. The swash plate 80 is protrusively formed with a hinge receiving section 81 hinge-coupled to the hinge section 71 of the rotor 70. The hinge receiving section 81 of the swash plate 80 is hinge-coupled to the hinge section 71 of the rotor 70 by a hinge pin 72, thereby allowing the swash plate 80 to rotate along with rotation of the rotor 70.
The swash plate 80 is connected to the individual pistons 23 by shoes 82. Refrigerant is introduced into or compressed and discharged from the cylinder bore 22 while the pistons 23 linearly reciprocate within the cylinder bores 22 by rotation of the swash plate 80.
In this case, the swash plate 80 is installed such that an angle of the swash plate 80 is variable according to the rotary shaft 30, so as to enable a discharge amount of refrigerant in the compressor 10 to be regulated. To this end, an opening degree of a passage (not shown), which allows the discharge chamber 51 to communicate with the crank chamber 41, is adjusted by a pressure regulation valve (not shown), and thus an inclined angle of the swash plate 80 is changed by a change in pressure in the crank chamber 41.
The variable swash plate compressor having the above configuration is disclosed in Korean Patent Laid-Open Publication No. 10-2003-0048228 (Jun. 19, 2003) and Korean Patent Publication No. 10-125976 (Apr. 24, 2013).
Hereinafter, the configuration of the valve assembly will be described in more detail.
The valve assembly includes a central valve plate, a suction reed plate installed on a cylinder block side surface of the valve plate, and a discharge reed plate installed on a rear housing side surface of the valve plate.
FIG. 2 is an exploded perspective view illustrating a conventional valve plate 60 and suction reed plate 63. Although not shown, the discharge reed plate is installed on the other side surface of the valve plate 60. The valve plate 60 is a metal plate having a disc shape and is formed with the discharge ports 61 and suction ports 62 corresponding to the respective cylinder bores 22.
A plurality of suction reeds 64 for opening and closing the suction ports 62 of the valve plate 60 is formed in a cut manner on the suction reed plate 63.
The discharge reed plate is formed wherein a plurality of discharge reeds for opening and closing the discharge ports 61 of the valve plate 60 is protrusively formed on an outer periphery of the circular plate covering portions at which the suction ports 62 of the valve plate 60 are formed.
FIG. 3 shows a portion of the valve assembly facing one cylinder bore 22. FIG. 3 shows one suction reed 64, one discharge reed 66, and one suction port 62 and discharge port 61 formed on the valve plate 60 in a state in which the suction reed plate 63, the valve plate 60, and the discharge reed plate are sequentially stacked. Reference numeral 53 is a partition wall formed in the rear housing 50 to partition the suction chamber 52 and the discharge chamber 51.
In the above state, when the piston is moved to a top dead center (suction stroke), a negative pressure is generated in the cylinder bore 22. Consequently, the suction reed 64 opens the suction port 62 while being bent about base end portions 64c of leg sections 64b toward the cylinder bore 22 so that refrigerant in the suction chamber 52 is introduced into the cylinder bore 22 through the suction port 62. In this case, the discharge reed 66 closes the discharge port 61 so that the refrigerant is smoothly introduced through the suction port 62.
Subsequently, when the piston is moved to a bottom dead center (compression stroke), the suction reed 64 is returned to an original position by a compressed refrigerant pressure so as to close the suction port 62. In this case, the refrigerant pressure acts on the discharge reed 66 through an opening hole 64a of the suction reed 64 and the discharge port 61, and thus the discharge reed 66 opens the discharge port 61 while being pushed toward the discharge chamber 51 so that the refrigerant in the cylinder bore 22 is discharged to the discharge chamber 51 through the discharge port 61.
Meanwhile, refrigerant should be rapidly introduced into and discharged from the cylinder bore 22, in order to enhance performance of the compressor. However, when the compressor is merely driven at high speed for increasing a flow rate of refrigerant, there are problems in that noise and pulsation are increased and durability of the compressor is deteriorated.
When the compressor 10 is operated, the suction reed 64 performs an opening and closing operation at a rate of once per one revolution of the rotary shaft 30. Thus, the suction reed 64 performs the opening and closing operation at high speed at a rate of ten times to several hundred times per second according to the operation speed of the compressor 10.
Accordingly, the base end portion 64c of the leg section 64b of the suction reed 64, namely a connection portion between the suction reed 64 and the suction reed plate 63, is repeatedly folded and unfolded.
According to a result of analyzing stress distribution of the suction reed 64, it may be seen that a stress is concentrated on the base end portion 64c. In this case, a maximum principal stress applied to the base end portion 64c reaches about 436.69 Mpa.
In addition, since both leg sections 64b of the suction reed 64 are arranged in parallel with each other, the leg sections 64b have a weak structure in a torsional load acting on the suction reed 64 during the opening and closing operation thereof.
Thus, when fatigue is accumulated due to the repeated opening and closing operation of the suction reed 64, the base end portion 64c may be easily broken. Since the suction reed 64 is not normally operated when the base end portion 64c is broken, the refrigerant is not normally introduced through the suction port 62 of the valve plate 60. Consequently, since the refrigerant is not normally compressed and discharged, the compressor 10 may not be operated.